Composite high frequency component and mobile communication apparatus incorporating the same

ABSTRACT

A composite high frequency component and a mobile communication apparatus incorporating the same which needs no matching circuits and can easily be miniaturized. The composite high frequency component is constituted of a diplexer, high frequency switches, high frequency filters, and surface acoustic wave filters. The diplexer is formed by first inductors and first capacitors. The high frequency switches are formed by diodes, second inductors, and second capacitors. The high frequency filters are formed by third inductors and third capacitors.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. patent application Ser. No. 09/672,715,filed Sep. 28, 2000, now U.S. Pat. No. 6,445,262, in the name of KojiTANAKA, Koji FURUTANI, Takahiro WATANABE, Hideki MUTO, Takanori UEJIMAand Norio NAKAJIMA and entitled COMPOSITE HIGH FREQUENCY COMPONENT ANDMOBILE COMMUNICATION APPARATUS INCORPORATING THE SAME.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to composite high frequency components andmobile communication apparatuses incorporating the same. Moreparticularly, the invention relates to composite high frequencycomponents usable in a plurality of different mobile communicationsystems, and mobile communication apparatuses incorporating the same.

2. Description of the Related Art

Currently, in Europe, as mobile communication apparatuses, dual-bandmobile telephones are provided. Such an apparatus can be operated in aplurality of communication systems using different frequency bands, forexample, in a combination of the Digital Cellular System (DCS) using the1.8 GHz band and the Global System for Mobile Communications (GSM) using900 MHZ.

FIG. 10 shows a block diagram of a part of the structure of aconventional dual-band mobile telephone. It is an example in which theDCS using the 1.8 GHz band and the GSM using the 900 MHZ band arecombined. The dual-band mobile telephone has an antenna 1, a diplexer 2,and two signal paths DCS and GSM.

The diplexer 2 selects signals transmitted from the DCS and the GSM atthe time of transmission, and selects signals received in the DCS andthe GSM at the time of reception. The DCS side is constituted of a highfrequency switch 3 a dividing the signal path into a transmissionsection Txd and a reception section Rxd, a high frequency filter 3 battenuating second-order harmonic signals and third-order harmonicsignals on the DCS side, and a surface acoustic wave filter 3 cpreventing entering of the transmitted signals into the receptionsection Rxd. The GSM side is constituted of a high frequency switch 4 adividing the signal path into a transmission section Txg and a receptionsection Rxg, a high frequency filter 4 b attenuating third-orderharmonic signals on the GSM side, and a surface acoustic wave filter 4 cpreventing entering of the transmitted signals into the receptionsection Rxg.

Now, a description will be given of the operation of the dual-bandmobile telephone by using the example of the DCS side. When a signal istransmitted, the high, frequency switch 3 a makes a circuit to thetransmission section Txd to send the signal transmitted from thetransmission section Txd to the high frequency filter 3 b. The diplexer2 selects the signal passed through the high frequency filter 3 b totransmit from the antenna 1. When a signal is received, the signalreceived in the antenna 1 is selected by the diplexer 2 to be sent tothe high frequency filter 3 b. The high frequency switch 3 a makes acircuit to the reception section Rxd to send the signal passed throughthe high frequency filter 3 b to the reception section Rxd via thesurface acoustic wave filter 3 c. In the GSM side, signals are alsotransmitted and received by the same operation.

However, in the conventional dual-band mobile telephone, the antenna,the diplexer, the high frequency switches in the DCS and the GSM sides,the high frequency filters, and the surface acoustic wave filters areindependently mounted on a circuit board. As a result, in order toobtain matching characteristics, attenuation characteristics, andisolation characteristics, it is necessary to add matching circuitsbetween the diplexer and the high frequency switches, between the highfrequency switches and the high frequency filters, and between the highfrequency switches and the surface acoustic wave filters, respectively.Thus, since the number of components and the area required for disposingthe components are increased, the size of the circuit board is alsoincreased. This leads to an increase in the size of the dual-band mobiletelephone.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides acomposite high frequency component in which no matching circuits arenecessary and a circuit board for mounting components can beminiaturized, and a mobile communication apparatus incorporating thesame.

According to a first aspect of the present invention, there is provideda composite high frequency component included in a microwave circuithaving a plurality of signal paths corresponding to respectivefrequencies. The composite high frequency component includes a diplexerwhich accepts signals transmitted from the corresponding plurality ofsingle paths at a time of transmission, and delivers received signals tothe plurality of signal paths at a time of reception; a plurality ofhigh frequency switches dividing the plurality of signal paths intorespective transmission sections and reception sections; a plurality ofhigh frequency filters connected in respective signal paths; a pluralityof surface acoustic wave filters connected to the reception-sectionsides at the rear of the corresponding plurality of high frequencyswitches; and a multi-layer substrate formed by laminating a pluralityof ceramic sheet layers to integrate the diplexer, the high frequencyswitches, the high frequency filters, and the surface acoustic wavefilters.

In addition, in the composite high frequency component, the plurality ofhigh frequency filters may be connected to the transmission-sectionsides either at the front or at the rear of the corresponding pluralityof high frequency switches.

In addition, in the composite high frequency component, the plurality ofhigh frequency filters may be notch filters.

Furthermore, the above composite high frequency component may furtherinclude first inductance elements and first capacitance elements to formthe diplexer; switching elements, second inductance elements, and secondcapacitance elements to form each of the plurality of high frequencyswitches; and a third inductance element and third capacitance elementsto form each of the plurality of high frequency filters. In addition,the composite high frequency component may further include connectingsections formed inside the multi-layer substrate to connect the surfaceacoustic wave filters, the switching elements, the first to thirdinductance elements, and the first to third capacitance elements, someof which are contained in the multi-layer substrate and the remainingconstituents are mounted thereon.

In this composite high frequency component, the surface acoustic wavefilters may be mounted and sealed in a cavity formed inside themulti-layer substrate.

According to a second aspect of the present invention, there is provideda mobile communication apparatus including an antenna, a transmissionsection, a reception section, and the composite high frequency componentdescribed above.

In the above composite high frequency component, since the diplexer, thehigh frequency switches, the high frequency filters, and the surfaceacoustic wave filters constituting the composite high frequencycomponent are integrated by the multi-layer substrate formed bylaminating the plurality of ceramic sheet layers, connections betweenthese constituents can be disposed inside the multi-layer substrate.

As a result, matching adjustments can be easily made, by techniques wellknown to those ordinarily skilled in the art, between the diplexer andthe high frequency switches, between the high frequency switches and thehigh frequency filters, and between the high frequency switches and thesurface acoustic wave filters. Thus, it is unnecessary to disposematching circuits between the constituents.

Furthermore, since the mobile communication apparatus uses the compositehigh frequency component requiring no such matching circuits, thecircuit board, on which the microwave circuit having the plurality ofsignal paths is formed, can be miniaturized.

Other features and advantages of the invention will be understood fromthe following description of embodiments thereof, with reference to thedrawings in which like references denote like elements and parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a composite high frequency componentaccording to a first embodiment of the present invention;

FIG. 2 is a circuit diagram of a diplexer constituting the compositehigh frequency component shown in FIG. 1;

FIGS. 3A and 3B show circuit diagrams of high frequency switchesconstituting the high frequency component shown in FIG. 1;

FIGS. 4A4B show circuit diagrams of high frequency filters constitutingthe composite high frequency component shown in FIG. 1;

FIG. 5 is a partial exploded perspective view showing the detailedstructure of the composite high frequency component shown in FIG. 1;

FIGS. 6A to 6H are top views of a first sheet layer to an eighth sheetlayer;

FIGS. 7A to 7E are top views of a ninth sheet layer to a thirteenthsheet layer, and FIG. 7F is a bottom view of the thirteenth sheet layer;

FIG. 8 is a sectional view of a modified example of the composite highfrequency component shown in FIG. 5;

FIG. 9 is a block diagram of a composite high frequency componentaccording to a second embodiment of the present invention; and

FIG. 10 is a block diagram showing a part of the structure of aconventional dual-band mobile telephone as a mobile communicationapparatus.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Now, referring to the drawings, a description will be given of theembodiments of the present invention.

FIG. 1 shows a block diagram of a composite high frequency componentaccording to a first embodiment of the present invention. A compositehigh frequency component 10 is constituted of a diplexer 11, a highfrequency switch 121, a high frequency filter 122, and a surfaceacoustic wave filter 123, which form a DCS circuit (hereinafter “DCS”),and a high frequency switch 131, a high frequency filter 132, and asurface acoustic wave filter 133, which form a GSM circuit (hereinafter“GSM”). An area surrounded by dotted lines indicates a multi-layersubstrate (not shown), in which the above constituents are integrated.

An antenna ANT is connected to a first port P11 of the diplexer 11. Afirst port P31 d of the high frequency filter 122 of the DCS isconnected to a second port P12 of the diplexer 11. A first port P31 g ofthe high frequency filter 132 of the GSM is connected to a third portP13 of the diplexer 11.

In addition, on the DCS side, a first port P21 d of the high frequencyswitch 121 is connected to a second port P32 d of the high frequencyfilter 122. A transmission section Txd is connected to a second port P22d of the high frequency switch 121. Furthermore, a first port P41 d ofthe surface acoustic wave filter 123 is connected to a third port P23 dof the high frequency switch 121. A reception section Rxd is connectedto a second port P42 d of the surface acoustic wave filter 123.

On the GSM side, a first port P21 g of the high frequency switch 131 isconnected to a second port P32 g of the high frequency filter 132, and atransmission section Txg is connected to a second port P22 g of the highfrequency switch 131. Moreover, a first port P41 g of the surfaceacoustic wave filter 133 is connected to a third port P23 g of the highfrequency switch 131, and a reception section Rxg is connected to asecond port P42 g of the surface acoustic wave filter 133.

FIG. 2 is a circuit diagram of the diplexer 11 constituting thecomposite high frequency component shown in FIG. 1. The diplexer 11 isconstituted of first inductors L11 and L12 as first inductance elements,and first capacitors C11 to C15 as first capacitance elements.

Between the first port P11 and the second port P12 of the diplexer 11,first capacitors C11 and C12 are connected in series. The junction ofthe capacitors C11 and C12 is grounded via the first inductor L11 andthe first capacitor C13.

Between the first port P11 and the third port P13, a parallel circuitconstituted of the first inductor L12 and the first capacitor C14 isconnected, and the third port P13 of the parallel circuit is groundedvia the first capacitor C15.

A high pass filter is formed between the first port P11 and the secondport P12, and a notch filter (a band elimination filter) is formedbetween the first port P11 and the third port P13.

FIGS. 3A and 3B show circuit diagrams of the high frequency switches 121and 131 constituting the composite high frequency component shown inFIG. 1. FIG. 3A shows the circuit diagram of the high frequency switch121 of the DCS side, and FIG. 3B shows the circuit diagram of the highfrequency switch 131 of the GSM side. The high frequency switches 121and 131 have the same circuit structures. Thus, only the high frequencyswitch 121 will be described in the following description, which willalso give the reference numbers of the corresponding structural parts ofthe high frequency switch 131.

The high frequency switch 121 (131) is constituted of diodes D1 d (D1 g)and D2 d (D2 g) as switching elements, second inductors L21 d to L23 d(L21 g to L23 g) as second inductance elements, and second capacitorsC21 d to C23 d (C21 g to C23 g) as second capacitance elements. Thesecond inductor L21 d (L21 g) is a parallel trap coil, and the secondinductor L22 d (L22 g) is a choke coil.

The diode D1 d (D1 g) is connected between the first port P21 d (P21 g)and the second port P22 d (P22 g) in such a manner that the cathode ofthe diode D1 d (or D1 g) is oriented toward the first port P21 d (P21g). The diode D1 d (D1 g) is connected in parallel to a series circuitconstituted of the second inductor L21 d (L21 g) and the capacitor C21 d(C21 g).

The anode of the diode D1 d (D1 g), which is oriented toward the secondport P22 d (P22 g), is grounded via the second inductor L22 d (L22 g)and the second capacitor C22 d (C22 g). A control terminal Vcd (Vcg) isconnected to the junction of the second inductor L22 d (L22 g) and thesecond capacitor C22 d (C22 g).

The second inductor L23 d (L23 g) is connected between the first portP21 d (21 g) and the third port P23 d (P23 g), and the third port P23 dof the second inductor L23 d (L23 g) is grounded via the diode D2 d (D2g) and the second capacitor C23 d (C23 g). The junction of the cathodeof the diode D2 d (D2 g) and the second capacitor C23 d (C23 g) isgrounded via a resistor Rd (Rg).

FIGS. 4A and 4B show circuit diagrams of the high frequency filters 122and 132 constituting the composite high frequency component shown inFIG. 1. FIG. 4A shows the high frequency filter 122 on the DCS side, andFIG. 4B shows the high frequency filter 132 on the GSM side. Since thehigh frequency filters 122 and 132 have the same circuit structures, thehigh frequency filter 122 will be described, and only the referencenumbers of the corresponding structural parts of the high frequencyfilter 132 will be given.

The high frequency filter 122 (132) is constituted of a third inductorL31 d (L31 g) as a third inductance element and third capacitors C31 dto C32 d (C31 g and C32 g) as third capacitance elements.

The third inductor L31 d (L31 g) is connected between the first port P31d (P31 g) and the second port P32 d (P32 g), and the third capacitor C31d (C31 g) is connected in parallel to the third inductor L31 d (L31 g).

The second port P32 d (P32 g) of the third inductor L31 d (L31 g) isgrounded via the third capacitor C32 d (C32 g).

As described above, the high frequency filters 122 and 132 form notchfilters by the third inductor L31 d (L31 g) and the third capacitors C31d and C32 d (C31 g and C32 g).

FIG. 5 is a partial exploded perspective view showing the detailedstructure of the composite high frequency component 10 shown in FIG. 1.The composite high frequency component 10 includes a multi-layersubstrate 14. In the multi-layer substrate 14 are contained firstinductors L11 and L12 and first capacitors C11 to C15 constituting thediplexer 11 shown in FIG. 2, second inductors L21 d, L23 d, L21 g, andL23 g, and second capacitors C21 d, C22 d, C21 g, and C22 g constitutingthe high frequency switches 121 and 131shown in FIGS. 3A-3B, thirdinductors L31 d and L31 g, and third capacitors C31 d, C32 d, C31 g, andC32 g constituting the high frequency filters 122 and 132 shown in FIGS.4A-4B, although the diplexer 11, the high frequency switches 121 and131, and the high frequency filters 122 and 132 are not shown in FIG. 5.

On a surface of the multi-layer substrate 14 are mounted surfaceacoustic wave filters 123 and 133 in the form of chips, with the diodesD1 d, D2 d, D1 g, and D2 g, the second inductors (choke coils) L22 d andL22 g, the second capacitors C23 d and C23 g, and the resistors Rd andRg constituting the high frequency switches 121 and 131 shown in FIGS.3A and 3B.

In addition, from the side surfaces to the bottom surface of themulti-layer substrate 14, twelve external terminals Ta to Tl are formedby screen printing or the like. Among the external terminals Ta to Tl,the five external terminals Ta to Te are disposed on one longerside-surface of the multi-layer substrate 14, the five externalterminals Tg to Tk are disposed on the other longer side-surfacethereof. The remaining two external terminals Tf and Tl are disposed onthe mutually opposing shorter side-surfaces thereof.

Then, a metal cap 15 is disposed to cover the multi-layer substrate 14in such a manner that the constituents disposed on the substrate 14 arecovered and protrusions 151 and 152 on the mutually opposing shorterside-surfaces abut with the external terminals Tf and Tl.

The external terminals Ta to Tl are used as the first port P11 of thediplexer 11, the second ports P22 d and P22 g of the high frequencyswitches 121 and 131, the control terminals Vcd and Vcg of the highfrequency switches 121 and 131, the second ports P42 d and P42 g of thesurface acoustic wave filters 123 and 133, and grounds.

Inside the multi-layer substrate 14, the second port P12 of the diplexer11 is connected to the first port P31 d of the high frequency filter122, the second port P32 d of the high frequency filter 122 is connectedto the first port P21 d of the high frequency switch 121, the third portP23 d of the high frequency switch 121 is connected to the first portP41 d of the surface acoustic wave filter 123, the third port P13 of thediplexer 11 is connected to the first port P31 g of the high frequencyfilter 132, and the third port P23 g of the high frequency switch 131 isconnected to the first port P41 g of the surface acoustic wave filter133.

FIGS. 6A to 6H, and FIGS. 7A to 7F show the top views and bottom viewsof sheet layers forming the multi-layer substrate 14 of the compositehigh frequency component shown in FIG. 5. The multi-layer substrate 14is formed by laminating first to thirteenth sheet layers 14 a to 14 mfrom above in sequence and then cofiring them at temperatures of equalto or less than 1000 degrees. Each of the sheet layers is formed of aceramic material whose main components include barium oxide, aluminumoxide, and silica.

On the top surface of the first sheet layer 14 a, a plurality of lands,indicated collectively by La in the figures, are printed by screenprinting to be formed thereon. On the lands La are mounted the surfaceacoustic wave filters 123 and 133, the diodes D1 d, D2 d, D1 g, and D2g, the second inductors L22 d and L22 g, the second capacitors C23 d andC23 g, and the resistors Rd and Rg disposed on the surface of themulti-layer substrate 14.

On the top surfaces of the third and tenth sheet layers 14 c and 14 j,stripline electrodes SL1 to SL8 formed of conductive layers are printedby screen printing to be formed thereon. In addition, on the topsurfaces of the fourth to eighth sheet layers 14 d to 14 h and thetwelfth sheet layer 141, capacitor electrodes Cp1 to Cp18 formed ofconductive layers are printed by screen printing to be formed thereon.

On the top surfaces of the seventh, ninth, eleventh, and thirteenthsheet layers 14 g, 14 i, 14 k, and 14 m, ground electrodes G1 to G4formed of conductive layers are printed by screen printing to be formedthereon. Moreover, on the bottom surface of the thirteenth sheet layer14 m shown in FIG. 7f, the external termninals Ta to Tl are printed byscreen printing to be formed thereon.

On specified positions of the first to eleventh sheet layers 14 a to 14k, via-hole electrodes VHa to VHk for connecting the land La, thestripline electrodes SL1 to SL8, and the ground electrodes G1 to G4 aredisposed.

In this case, the first inductors L11 and L12 of the diplexer 11 areformed by the stripline electrodes SL6 and SL7. The second inductors L21d and L23 d of the high frequency switch 121 are formed by the striplineelectrodes SL2 and SL4. The second inductors L21 g and L23 g of the highfrequency switch 131 are formed by the stripline electrodes SL1 and SL3.

The third inductor L31 d of the high frequency filter 122 is formed bythe stripline electrode SL8. The third inductor L31 g of the highfrequency filter 132 is formed by the stripline electrode SL5.

The first capacitor C11 of the diplexer 11 is formed by the capacitorelectrodes Cp6 and Cp9. The first capacitor C12 is formed by thecapacitor electrodes Cp3 and Cp6. The first capacitor C13 is formed bythe capacitor electrode Cp17 and the ground electrode G4. The firstcapacitor C14 is formed by the capacitor electrodes Cp9 and Cp11. Thefirst capacitor C15 is formed by the capacitor electrode Cp16 and theground electrode G4.

The second capacitor C21 d of the high frequency switch 121 is formed bythe capacitor electrodes Cp5 and Cp8. The second capacitor C22 d thereofis formed by the capacitor electrode Cp13 and the ground electrode G2.The second capacitor C21 g of the high frequency switch 131 is formed bythe capacitor electrodes Cp4 and Cp7. The second capacitor C22 g thereofis formed by the capacitor electrode Cp13 and the ground electrode G2.

The third capacitor C31 d of the high frequency filter 122 is formed bythe capacitor electrodes Cp8 and Cp12. The third capacitor C32 d thereofis formed by the capacitor electrode Cp18 and the ground electrode G4.The third capacitor C31 g of the high frequency filter 132 is formed bythe capacitor electrodes Cp7 and Cp10. The third capacitor C32 g thereofis formed by the capacitor electrode Cp15 and the ground electrode G4.

Now, a description will be given of the operation of the composite highfrequency component 10 having the structure shown in FIG. 1. First, whena DCS signal (1.8 GHz band) is transmitted, the high frequency switch121 on the DCS side applies 3V to the control terminal Vcd to turn onthe diodes D1 d and D2 d. The transmitted signal on the DCS side passesthrough the high frequency switch 121, the high frequency filter 122,and the diplexer 11 to be transmitted from an antenna ANT connected tothe first port P11 of the diplexer 11.

In this case, the high frequency switch 131 on the GSM side applies 0Vto the control terminal Vcg to turn off the diode D1 g so that areceived GSM signal is not transmitted. In addition, with the diplexer11 connected to the DCS side and the GSM side, the transmitted signal onthe DCS side does not enter the transmission section Txg and receptionsection Rxg of the GSM side. The high frequency filter 122 of the DCSside attenuates the second-order and third-order harmonic signals on theDCS side.

Next, when a GSM signal (900 MHZ band) is transmitted, the highfrequency switch 131 on the GSM side applies 3V to the control terminalVcg to turn on the diodes D1 g and D2 g so that the transmitted GSMsignal passes through the high frequency switch 131, the high frequencyfilter 132, and the diplexer 11. The passed signal is transmitted fromthe antenna ANT connected to the first port P11 of the diplexer 11.

In this situation, the high frequency switch 121 on the DCS side applies0V to the control terminal Vcd to turn off the diode D1 d so that DCSsignals are not transmitted. In addition, with the diplexer 11 connectedto the DCS side and the GSM side, transmitted GSM signals do not enterthe transmission section Txd and reception section Rxd on the DCS side.The high frequency filter 132 on the GSM side attenuates the third-orderharmonic signals on the GSM side.

When both DCS and GSM signals are received, the high frequency switch121 on the DCS side applies 0V to the control terminal Vcd to turn offthe diodes D1 d and D2 d, and the high frequency switch 131 on the GSMside applies 0V to the control terminal Vcg to turn off the diodes D1 gand D2 g, whereby the received DCS signals do not enter the transmissionsection Txd of the DCS, and the received GSM signals do not enter thetransmission section Txg of the GSM.

In addition, with the diplexer 11 connected to the DCS and GSM sides,the received signals on the DCS side do not go to the GSM side, and thereceived signals on the GSM side do not go to the DCS side.

FIG. 8 is a sectional view of a modified example of the composite highfrequency component 10 shown in FIG. 5. In a composite high frequencycomponent 10-1, unlike the composite high frequency component 10 of thefirst embodiment shown in FIG. 5, surface acoustic wave filters 123 and133 are mounted in a cavity 15 formed inside a multi-layer substrate14-1.

When the multi-layer substrate 14-1 is formed, the cavity 15 is formedby laminating a sheet layer (not shown) having an opening in a positionfor forming the cavity 15 at the top. The cavity 15 is sealed by fillingresin 16 therein after the surface acoustic wave filters 123 and 133 aremounted therein.

In the composite high frequency component of the first embodiment, thediplexer, the high frequency switches, the high frequency filters, andthe surface acoustic wave filters constituting the composite highfrequency component are integrated in the multi-layer substrate formedby laminating the plurality of ceramic sheet layers. As a result,connections between the diplexer, the high frequency switches, the highfrequency filters, and the surface acoustic wave filters can beestablished inside the multi-layer substrate.

With this arrangement, matching adjustments can be easily made, bytechniques well known to those ordinarily skilled in the art, betweenthe diplexer and the high frequency switches, between the high frequencyswitches and the high frequency filters, and between the high frequencyswitches and the surface acoustic wave filters. Thus, no matchingcircuits for making the matching adjustments between the aboveconstituents are necessary.

Therefore, the composite high frequency component can be miniaturized.For example, the composite high frequency component with a metal cap canbe miniaturized so as to have dimensions of 6.7 mm×5.0 mm×2.0 mm.

Furthermore, since the high frequency filters are notch filters, it ispossible to attenuate only the signals of frequencies close to thesecond-order and third-order harmonics, which are desired to beattenuated. As a result, influence on the pass band of a fundamentalfrequency can be reduced. Therefore, as compared with cases in which theoverall harmonic frequency band is attenuated, as in low pass filtersand band pass filters, insertion losses in the pass band of thefundamental frequency can be reduced. Thus, insertion losses of theoverall composite high frequency component can be reduced.

Furthermore, in this composite high frequency component, the diplexer isformed by the first inductors and the first capacitors, the highfrequency switches are formed by the diodes, the second inductors, andthe second capacitor, and the high frequency filters are formed by thethird inductors and the third capacitors. Some of these constituents arecontained in the multi-layer substrate and the remaining constituentsare mounted thereon to be connected to each other by connecting sectionsformed inside the multi-layer substrate. With this arrangement, lossesdue to wiring between the constituents can be reduced. As a result,losses of the overall composite high frequency component can be reduced.

In addition, since the stripline electrodes which serve as inductors arecontained in the multi-layer substrate, wavelength-shortening effectspermit the lengths of the stripline electrodes as the inductors to beshortened. As a result, insertion losses of the stripline electrodes canbe reduced, thereby achieving miniaturization of the composite highfrequency component and reduction in insertion losses thereof.Accordingly, the mobile communication apparatus incorporating thecomposite high frequency component can be miniaturized, and can alsoobtain a high level of performance characteristics.

Furthermore, in the modified example shown in FIG. 8, since the surfaceacoustic wave filters are mounted and sealed in the cavity formed in themulti-layer substrate, bare chips can be used as the surface acousticwave filters. As a result, the size of the composite high frequencycomponent can be more reduced.

FIG. 9 shows a block diagram of a composite high frequency componentaccording to a second embodiment of the present invention. In acomposite high frequency component 20, unlike the composite highfrequency component 10 according to the first embodiment as shown inFIG. 1, the positions for connecting high frequency filters 122 and 132are changed.

In short, the DCS high frequency filter 122 is connected to atransmission section Txd at the rear of the high frequency switch 121.The GSM high frequency filter 132 is connected to a transmission sectionTxg at the rear of the high frequency switch 131.

In the composite high frequency component according to the secondembodiment described above, since each of the high frequency filters isconnected to the transmission section situated at the rear of each ofthe high frequency switches, when signals are transmitted, distortion ofsignals due to a high output amplifier in the transmission section canbe attenuated by the high frequency filter. As a result, insertionlosses in the reception section can be reduced.

In the second embodiment, the composite high frequency component hasbeen used for a combination of the DCS and GSM systems. However, thepresent invention is not limited to this combination, and can be appliedto other combinations, for example, a combination of the PersonalCommunication Services (PCS) and Advanced Mobile Phone Services (AMPS),a combination of the Digital European Cordless Telephone (DECT) and GSM,and a combination of the Personal Handy-phone System (PHS) and thePersonal Digital Cellular (PDC), and the like.

Although the above embodiments have described the cases of signal pathscorresponding to two systems, the same advantages can also be obtainedin cases of signal paths of three or more systems.

In addition, chip coils can be used as the parallel trap coils and chokecoils of the high frequency switches to be mounted on the multi-layersubstrate. In this case, since the parallel trap coils and the chokecoils are chip coils having high Q factors, chip coils having the sameconfigurations can be used in a plurality of systems having differentfrequency bands. As a result, modifications of design due to changes ofthe frequency bands can be easily made, whereby modification of designcan be made in a short time. Thus, production cost can be reduced.Moreover, since the parallel trap coils and the choke coils have higherQ factors, the pass band can be broadened and insertion losses can bemore reduced.

As described above, in the composite high frequency component, thediplexer, the high frequency switches, the high frequency filters, andthe surface acoustic wave filters, which form the composite highfrequency component, are integrated in the multi-layer substrate formedby laminating the plurality of ceramic sheet layers. With thisarrangement, connections between the diplexer, the high frequencyswitches, the high frequency filters, and the surface acoustic wavefilters, can be established inside the multi-layer substrate.

As a result, matching adjustments can be easily made by known techniquesbetween the diplexer and the high frequency switches, between the highfrequency switches and the high frequency filters, between the highfrequency switches and the surface acoustic wave filters. Accordingly,there is no need for matching circuits making matching adjustmentsbetween these constituents.

Therefore, since the number of constituents can be reduced, the circuitboard, on which the microwave circuit having the plurality of signalpaths is formed, can be miniaturized.

In the composite high frequency component, since the highfrequency-filters are connected to the transmission-section side at therear of the high frequency switches, distortion of transmitted signalsdue to the high output amplifier in the transmission section can beattenuated. As a result, insertion losses in the reception section canbe reduced.

In addition, since the high frequency filters are notch filters, it canbe arranged to attenuate only the signals of frequencies close to thesecond-order harmonic and the third-order harmonic, which are desired tobe attenuated. As a result, influence on the pass band of thefundamental frequency can be reduced. Therefore, as compared with thecases in which signals of the overall harmonic frequency bands areattenuated as in low pass filters and band pass filters, insertionlosses in the pass band of the fundamental frequency can be reduced.Accordingly, loss in the overall composite high frequency component canbe reduced.

The diplexer included in this composite high frequency component isformed by the first inductance elements and the first capacitanceelements, the plurality of high frequency switches is formed by theswitching elements, the second inductance elements, and the secondcapacitance elements, and the plurality of high frequency filters isformed by the third inductance elements and the third capacitanceelements. In addition, some of these constituents are contained in themulti-layer substrate and the remaining constituents are mounted thereonto be connected to each other by the connecting sections formed insidethe multi-layer substrate. With this arrangement, the composite highfrequency component can be constituted by using the single multi-layersubstrate, thereby leading to miniaturization of the composite highfrequency component. Furthermore, since losses due to wiring between theconstituents can be reduced, loss of the overall composite highfrequency component can be reduced.

In addition, since some of the stripline electrodes serving as inductorsare contained in the multi-layer substrate and the remaining striplineelectrodes are mounted thereon, wavelength-shortening effects permit thelengths of the stripline electrodes serving as the inductors to bereduced. Thus, since insertion loss of the stripline electrodes can bereduced, the size and loss of the composite high frequency component canbe reduced. As a result, the mobile communication apparatusincorporating the composite high frequency component can beminiaturized, and a high level of performance characteristics can besimultaneously obtained.

Moreover, since the surface acoustic wave filters are mounted and sealedin the cavity formed in the multi-layer substrate, bare chips can beused as the surface acoustic wave filters. As a result, the compositehigh frequency component can be more miniaturized.

In the mobile communication apparatus according to the presentinvention, since the compact composite high frequency component havingreduced loss is incorporated, the mobile communication apparatusincorporating the composite high frequency component can also beminiaturized and a high level of performance characteristics thereof canbe obtained.

While embodiments of the present invention have been described, it willbe understood that various modifications and changes may be made thereinwithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A composite high frequency component comprising:a diplexer which accepts transmitted signals from a plurality of signalpaths at a time of transmission, and delivers received signals to theplurality of signal paths at a time or reception; a plurality of highfrequency switches dividing the plurality of signal paths, respectively,into transmission sections and reception sections; a high frequencyfilter connected in at least one of the signal paths; a surface acousticwave filter connected to a respective one of the reception sections atthe rear of the corresponding high frequency switch; and a multi-layersubstrate comprising a plurality of laminated sheet layers in which thediplexer, the high frequency switches, the high frequency filter, andthe surface acoustic wave filter are interconnected, the multi-layersubstrate having a top surface and a bottom surface; wherein themulti-layer substrate includes a ground electrode formed on one of saidsheet layers adjacent to the bottom surface of the multi-layersubstrate, and the surface acoustic wave filter is mounted on the topsurface of the multi-layer substrate.
 2. The composite high frequencycomponent according to claim 1, wherein the composite high frequencycomponent comprises a plurality of high frequency filters including saidhigh frequency filter, and the plurality of high frequency filters areconnected in the respective transmission sections at the rear of thecorresponding plurality of high frequency switches.
 3. The compositehigh frequency component according to claim 2, wherein the plurality ofhigh frequency filters are notch filters.
 4. The composite highfrequency component according to claim 1, wherein: the diplexercomprises a first inductance element and a first capacitance element;each of the plurality of high frequency switches comprises a switchingelement, a second inductance element, and a second capacitance element;the high frequency filter comprises a third inductance element and athird capacitance element; and connections are formed inside themulti-layer substrate to connect the surface acoustic wave filter, theswitching element, the first to third inductance elements, and the firstto third capacitance elements, at least some of which are contained inthe multi-layer substrate and at least some of which are mountedthereon.
 5. The composite high frequency component according to claim 1,wherein the surface acoustic wave filter is sealed in a cavity formedinside the multi-layer substrate.
 6. The composite high frequencycomponent according to claim 1, wherein the high frequency filtercomprises a inductance element, a non-grounded capacitance element and agrounded capacitance element.
 7. The composite high frequency componentaccording to claim 6, wherein the grounded capacitance element of thehigh frequency filter is formed between the ground electrode formed onthe sheet layer adjacent to the bottom surface of the multi-layersubstrate and an electrode which is opposed to the ground electrode. 8.A mobile communication apparatus comprising transmission circuits andreception circuits, a transmission and a reception circuit beingconnected respectively to the transmission section and the receptionsection of each of said plurality of signal paths in the composite highfrequency component according to claim
 1. 9. The mobile communicationapparatus according to claim 8, further comprising an antenna connectedto said diplexer.
 10. A composite high frequency component for beingincluded in a microwave circuit having a plurality of signal pathscorresponding to respective frequencies, the composite high frequencycomponent comprising: a diplexer which accepts transmitted signals fromthe plurality of signal paths at a time of transmission, and deliversreceived signals to the plurality of signal paths at a time ofreception; a plurality of high frequency switches dividing the pluralityof signal paths, respectively, into transmission sections and receptionsections; a high frequency filter connected in a respective one of thesignal paths; at least one surface acoustic wave filter connected to arespective one of the reception sections at the rear of thecorresponding high frequency switch; and a multi-layer substratecomprising a plurality of laminated ceramic sheet layers in which thediplexer, the high frequency switches, the high frequency filter, andthe at least one surface acoustic wave filter are interconnected.
 11. Acomposite high frequency component according to claim 10, wherein saidhigh frequency filter is connected between the diplexer and acorresponding one of said plurality of high frequency switches of saidsignal path.
 12. A composite high frequency component according to claim10, wherein the high frequency filter is connected in the transmissionsection at the rear of the corresponding high frequency switch.
 13. Acomposite high frequency component according to claim 10, wherein thehigh frequency filter is a notch filter.
 14. A composite high frequencycomponent according to claim 10, wherein: the diplexer comprises firstinductance elements and first capacitance elements; each of theplurality of high frequency switches comprises switching elements,second inductance elements, and second capacitance elements; the highfrequency filter comprises a third inductance element and thirdcapacitance elements; and connections are formed inside the multi-layersubstrate to connect the at least one surface acoustic wave filter, theswitching elements, the first to third inductance elements, and thefirst to third capacitance elements, at least some of which arecontained in the multi-layer substrate and at least some of which aremounted thereon.
 15. A composite high frequency component according toclaim 10, wherein the at least one surface acoustic wave filter issealed in a cavity formed inside the multi-layer substrate.
 16. A mobilecommunication apparatus comprising a transmission circuit and areception circuit, said transmission and reception circuits beingconnected respectively to the transmission section and the receptionsection of each of said plurality of signal paths in the composite highfrequency component according to claim
 10. 17. A mobile communicationapparatus according to claim 16, further comprising an antenna connectedto said diplexer.
 18. A composite high frequency component according toclaim 10, wherein the multi-layer substrate includes a ground electrodeformed on one of said sheet layers adjacent to the bottom surface of themulti-layer substrate, and the at least one surface acoustic wave filteris mounted on the top surface of the multi-layer substrate.
 19. Acomposite high frequency component according to claim 18, wherein thehigh frequency filter comprises a inductance element, a non-groundedcapacitance element and a grounded capacitance element.
 20. A compositehigh frequency component according to claim 19, wherein the groundedcapacitance element of the high frequency filter is formed between theground electrode formed on the sheet layer adjacent to the bottomsurface of the multi-layer substrate and an electrode which is opposedto the ground electrode.